(1) Field of the Invention
The invention relates to a method of metallization in the fabrication of integrated circuits, and more particularly, to a method of increasing the electromigration lifetime of a tungsten plug in the manufacture of integrated circuits.
(2) Description of the Prior Art
Performance and cost constantly drive attempts to design increased performance while simultaneously shrinking feature sizes, particularly in interconnects. An example of increased design performance is the addition of a reservoir to the cathode end of an interconnect to increase electromigration lifetime by relying on the well known dependence of electromigration average lifetime with reservoir area. U.S. Pat. No. 5,506,450 to Lee et al, U.S. Pat. No. 5,864,179 to Koyama, and U.S. Pat. No. 5,760,477 to Cronin disclose extended end portions of the top Aluminum line over the tungsten plug to act as an aluminum reservoir. U.S. Pat. No. 5,654,216 to Adrian teaches a double aluminum line over a tungsten plug. U.S. Pat. No. 5,834,369 to Murakami et al discloses a diffusion preventing film over a tungsten plug to allow for an alignment margin.